#!/usr/bin/env python3
'''
计算派值
'''
num = 1000000000
while num > 100000:
    num = input('输入数字')
    num = int(num)

sum = 0
for i in range(1,num+1,1):
    sum = sum + 1/i**2
sum = sum * 6
sum = sum**0.5
print('计算派值为：',sum)